Inquiry turns to Boston Marathon bombing suspect’s wife

Federal law enforcement officials are sharpening their focus on the widow of the dead suspect in the Boston Marathon bombings after finding al-Qaida’s Inspire magazine and other radical Islamist material on her computer, according to law enforcement officials.

The probe of the computer belonging to Katherine Russell, 24, the widow of Tamerlan Tsarnaev, is part of the effort by investigators to determine whether Russell knew anything about the April 15 bombing plot or helped the Tsarnaev brothers hide from authorities, according to the officials, who spoke on the condition of anonymity to discuss the ongoing investigation.

Dzhokhar Tsarnaev, 19, the surviving suspect, has told investigators that he and his brother learned to build the pressure-cooker bombs from the English-language Inspire magazine, and that they were partly influenced by the online sermons of Anwar al-Awlaki, the al-Qaida propagandist who was killed in a drone strike in Yemen in 2011.

According to officials, Dzhokhar Tsarnaev also told investigators that he and his brother built the bombs in Tamerlan Tsarnaev’s Cambridge apartment, where the elder brother lived with Russell and their daughter. Officials said that Russell called her husband when she saw his photograph on television – following the FBI’s release of the pictures of the suspects – but did not notify authorities.

One of the key questions for investigators is whether the radical Islamist materials on Russell’s computer belonged to her or were downloaded by her husband or someone else.

Russell’s attorney did not return phone calls for a comment. The attorney, Amato DeLuca, has previously said his client played no role in the plot and was shocked to learn of the involvement of the Tsarnaev brothers.

In another development, federal agents, state troopers and local law enforcement officers scoured a wooded area near Dartmouth, Mass., where Dzhokhar Tsarnaev attended college. Investigators are looking for possible evidence that might indicate the brothers tested explosives there, according to a law enforcement official. Residents in the vicinity had reported hearing loud noises coming from the woods March 30.

FBI spokesman Jason Pack said that the Dartmouth search by law enforcement and explosive-sniffing dogs is part of the continuing investigation into the bombings.

On Monday, FBI special agents spent about 90 minutes inside the North Kingstown, R.I., home of Russell’s parents. The agents left with bags of material and a sample of Russell’s DNA.

Two law enforcement officials said that investigators found fingerprints and female DNA on fragments of the pressure-cooker bombs that exploded at the marathon. The DNA could have come from a woman who helped the suspects make the bombs or from a person who handled the materials at a store where the suspects bought them, said the officials. The DNA may have also come from someone in the crowd at the marathon, one of the officials said.

Law enforcement officials said several “persons of interest” in the United States and Russia are being investigated in connection with the brothers. One of the primary focuses remains the seven months that Tamerlan Tsarnaev spent in strife-torn regions of southern Russia in 2012.

During 16 hours of questioning in the hospital by the FBI, the younger Tsarnaev told agents that he and his brother initially considered carrying out suicide bombings and executing their plot on the Fourth of July at Boston’s large celebration along the Charles River, two law enforcement officials said.

But Tsarnaev said that he and his brother decided to launch their attack earlier because they were able to assemble the bombs in three or four days, more quickly than they had expected, according to two law enforcement officials.

Officials have expressed some skepticism about Tsarnaev’s account, saying that the complexity of the bombs makes it unlikely that the brothers could have completed assembling them as fast as he claimed.

According to a government document obtained by NBC News, a detailed analysis of the bombs used at the Boston Marathon – and the pipe bombs allegedly thrown at the police from the Tsarnaevs’ car during a gunfight four days later – show striking similarities to instructions from Inspire magazine.

The report from the Terrorist Explosive Device Analytical Center (TEDAC) said that the design of the pressure cooker bombs and the pipe bombs resembled the instructions provided in an article in the first issue of Inspire headlined “Make a Bomb in the Kitchen of Your Mom.”

The pressure-cooker bombs use different triggers and power sources than the Inspire designs, but they match the magazine instructions in the use of several components, including gunpowder from fireworks, according to the TEDAC analysis.